Problem: Solve for $z$ : $-28 + z = -24$
Answer: Add $28$ to both sides: $ \begin{eqnarray} \\ -28 + z &=& -24 \\ \\ {+28} && {+28} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-28 + z} &\hphantom{=}& \hphantom{-24} \\ z &=& -24 {+ 28} \\ \end{eqnarray} $ Simplify. $ z = 4$